1. Field of the Invention
The present invention relates to a growth substrate and a light emitting device comprising the same.
2. Background of the Invention
A light emitting diode (LED) converts an electrical signal into light using characteristics of compound semiconductors. LEDs are now being applied to devices such as home appliances, remote controls, electronic signboards, displays, a variety of automatic appliances and the like and their application range continues to expand.
A light emitting device generally dissipates energy, in particular, in heat or light form corresponding to an energy gap between a conduction band and a valence band through a combination of electrons in an n-layer with holes in a p-layer by applying a forward voltage. Here, a device emitting the energy in light form is an LED.
A nitride semiconductor generally has a high thermal stability and wide band-gap energy, and thus attracts great interest in development of optical elements and high output electronic elements. Specifically, blue, green and UV light emitting devices and the like using nitride semiconductors are commercially available in a broad range of applications.
A light emitting device may be distorted due to a lattice mismatch between a substrate and a semiconductor layer or a plurality of semiconductor layers. Accordingly, there is a need for solving lattice mismatch while maintaining optical and electrical properties.
A gallium nitride material used for manufacturing blue light emitting diodes has a hexagonal crystal system (Wurzit) structure and a thin film is generally grown along a c-axis crystal direction. The most general reason for growing the thin film along the c-axis crystal direction is that horizontal growth of a gallium nitride thin film is easy in this crystal direction and high crystal qualities associated with reduction in defects such as dislocation are obtained.
When a hetero-thin film is grown on the substrate, piezoelectric polarization may be generated. Such a polarization produces an internal field and thereby deforms an active layer energy band structure. In order to solve this problem, there is a need for manufacturing light emitting diodes using a material having a crystal structure in a nonpolar direction causing no polarization phenomenon.